Understanding the interaction of concanavalin a with mannosyl glycoliposomes: a surface plasmon resonance and fluorescence study

Abstract

The specificity of carbohydrate-protein interaction is a key factor in many biological processes and it isthe foundation of technologies using glycoliposomes in drug delivery. The incorporation of glycolipidsin vesicles is expected to increase their specificity toward particular targets such as lectins; however,the degree of exposure of the carbohydrate moiety at the liposome surface is a crucial parameter to beconsidered in the interaction. Herein we report the synthesis of mannose derivatives with one or twohydrophobic chains of different length, designed with the purpose of modifying the degree of exposureof the mannose when they were incorporated into liposomes.The interaction of glycovesicles with Con A was studied using: (i) agglutination assays; measured bydynamic laser light scattering (DLS); (ii) time resolved fluorescence methods and (iii) surface plasmonresonance (SPR) kinetic measurements. DLS data showed that an increase in hydrophobic chain lengthpromotes a decrease of liposomes hydrodynamic radius. A longer hydrocarbon chain favors a deeperinsertion into the bilayer and mannose moiety results less exposed at the surface to interact with lectin.Fluorescence experiments showed changes in the structure of glycovesicles due to the interaction withthe protein. From SPR measurements the kinetic and equilibrium constants associated to the interactionof ConA with the different glycolipid synthetized were determined.The combination of SPR and fluorescence techniques allowed to study the interaction of Con A withmannosyl glycovesicles at three levels: at the surface, at the interface and deeper into the bilayer.